Residential concrete construction typically includes, for example, slab-on-grade floors for homes, basement floors, garage floors, sidewalks, patios, driveways and/or decorative concrete areas and/or the like. In some concrete slab applications, it is desirable to pre-stress the concrete to increase its load carrying capacity after it has been screeded and allowed to cure to the proper strength. Such an approach is known in the concrete industry as “post tensioned concrete” or “PT concrete”. Post tensioning of the concrete enables longer free spans of concrete between points of substantial support or vertical columns in the case of elevated slabs, and makes possible the placement of on-grade slabs over soft ground and areas that have loose or sandy subsoil conditions that may eventually allow the slabs to crack or fail under working loads over time. Post tensioning of concrete slabs typically results in elevated and on-grade concrete slabs that can withstand greater live or working loads than non-pre-stressed concrete.
In such post tensioning applications, specially installed tensioning cables may be disposed along and periodically spaced within the concrete slab along with typical steel wire mesh and rebar prior to the placement and leveling of the uncured concrete. After the concrete has been screeded, finished, and cured to a sufficient level of strength, the internal post tensioning cables are pulled and thus tensioned using specially designed jacking devices at the perimeter end-faces of the concrete slab. Once the cables are tensioned to a pre-determined amount of tensioning force, the ends of the cables are permanently secured to the perimeter end-faces of the concrete slab, transferring and evenly distributing the respective cable tension forces to the end faces of the slab. The jacking devices are then removed, maintaining the resulting compressive stresses generated within the cured concrete slab. The resulting compressive stresses within the concrete allow it to withstand significantly greater live working loads over time without cracking or potential failure occurring.
Typically, when screeding uncured concrete that includes post-tensioned cables, the use of manual screeding or hand-held screeding devices are preferred because such concrete screeding equipment does not tend to disturb the carefully placed and positioned post-tensioned cables that are installed to specific architectural and engineering dimensional specifications within the slab. The relatively greater weight of conventional structure-supported screeding equipment or wheeled equipment is likely to sink into the concrete, contacting and disturbing the locations of the post-tensioned cables within the uncured concrete. Use of such currently known and available automated and mechanized screeding machines on post tension concrete slabs is not recommended or even permitted in most instances. The excessive weight and complexity of these current state of the art machines can potentially interfere and disturb the post tensioning cables, and thus manual or hand-held screeding devices must typically be used. Such a manual screeding approach is known to be both labor intensive and time consuming.